This invention relates to concentrated aqueous, built liquid detergent compositions suitable for laundry or presoak formulations. More particularly, it relates to aqueous built liquid detergent compositions which are highly concentrated in surfactant and builder and are provided as homogeneous, clear single-phase liquid solutions.
The formulation of concentrated built aqueous liquid detergent compositions has been a commercial objective in the detergent art in recent years. It is generally required that such compositions provide good detergency at low product concentration in the bath, contain water as the principal solvent and are in the form of homogeneous single-phase solutions which provide long-term shelf life without undergoing phase separation. Conventional liquid detergent compositions containing a detergency builder are generally not highly concentrated. That is, they are formulated as relatively dilute aqueous solutions so as to solubilize the builder and surfactant in the liquid composition. To provide the desired detergency, relatively high concentrations of such product are needed in the bath.
The term "concentrated" as used herein refers to liquid detergent compositions which can provide effective detergency at a product concentration equivalent to about "1/4 cup" under U.S. washing conditions, namely about 60 ml of detergent composition per standard wash load (about 17 U.S. gallons for a top loading washing machine), which corresponds to a concentration of about 0.1% of liquid detergent composition in the wash bath. To achieve a commercially acceptable level of detergency at such low product concentration, it is necessary that a high proportion of the detergent composition be comprised of active ingredients, notably, surfactant and builder. Thus, the term "concentrated" liquid detergent as used herein, is defined as a detergent composition which contains no more than about 65%, by weight, water.
As a practical matter, it is important that water is used as the principal, is not the sole, solvent in such concentrated liquid detergent composition, avoiding the use of costly solvents such as glycols. Accordingly, the liquid detergent compositions described herein contain at a minimum about 35% water, by weight of the liquid composition, a water content of about 45% to 60% being ordinarily preferred.
Built liquid detergent compositions are known in the art. However, because of the limited solubility of builder and surfactant in water, such detergent compositions are generally prepared as relatively dilute aqueous compositions containing for the most part in excess of 65%, and often as high as 93%, by weight, water. Frequently, an alkylene glycol co-solvent is used to enhance the solubility of the built detergent composition. In those aqueous compositions which contain less than 65% water, the proportion of builder is generally kept low, i.e. no greater than about 10%, by weight, so as to enhance the solubility of the built detergent in water. To provide acceptable detergency when used under standard U.S. washing conditions, such known liquid compositions are conventionally used at product concentrations substantially above the "1/4 cup" concentration (about 0.1%, by weight) at which the liquid detergent compositions of the present invention are effective. Moreover, the conventional detergent compositions are generally in the form of emulsions or suspensions rather than forming clear homogeneous solutions which are stable against the phase separation.
The detergent compositions described in U.S. Pat. No. 3,912,662 to Martinsson et al and U.S. Pat. No. 4,021,377 to Borchert et al are illustrative of the prior art. The Martinsson et al patent discloses an aqueous detergent composition containing nonionic and betaine detergents and a polyphosphate builder. In example 1, a composition is described containing 66% water and 12% alkylene glycol as the solvent. The Borchert et al patent describes a phosphate-free liquid detergent composition containing citrate builder and surfactant in a water-glycol solvent. The amount of water in each of the seven compositions disclosed in Table 1 of the patent is less than 26%, by weight, the major portion of the solvent being an alkylene glycol. Consequently, the ability to provide an economical liquid detergent composition which utilizes water as the principal solvent yet is in the form of a concentrated clear single-phase solution remains as a problem yet to be overcome in formulating a commercially acceptable built concentrated liquid detergent composition.